You should be able to find it in the hidden menu. Open dialer and type *#*#4636#*#* That will open the testing menu. Select Phone information, smsc is all the at the bottom. It should appear blank. Taping refresh or update should automatically pull the correct one.

Having found the SMSC it won't populate when I press Update or Refresh.
So I put the numbers in manually but then what?
How do you get it to accept them so they stay there?
Mine always disappear if I press any other key?
edi